cold_beer839

Has anybody tried Red Line Synthetic ATF in their auto trans?

I have an '87 S4 with 83k miles. I'm going to service the trans and I'm trying to decide between synthetic or conventional ATF dexron III.

I have heard that using synthetic ATF in a higher mileage auto trans will cause shifting problems.

Then, on the other hand, I have been told that it will make shifting better.

Chime in with your experiences please.

docmirror

I have never used a synthetic lube in an auto trans. Here's the failure mode as it was explained to me. Over time, the clutches in the trans become lightly coated with tarnish from the dino trans fluid. This is normal, and the bands adjust to the coating on the clutch plates. If the trans is then flushed and filled with a high slip syn fluid, it tends to wash the coating off the clutches, and they do not engage as well, ultimately causing slippage and failure to shift.

The only solution I've heard is to partially drain the old fluid, and refill with normal fluid. Don't drain the entire trans, but do this a few times to exchange most of the fluid. This is what I've sen happen on older US trans. The 928/MB unit may be different, but it makes sense.

Brett928S2

Hi

For what its worth...when I fitted my Nitrous , at first the autobox was ok, then as my hp was increased past 150 hp of Nitrous (roughly 500 hp in total)...the autofluid started "boiling" (by boiling I mean badly overheating...I could SMELL the burnt fluid) and shifting from a launch was awful..didnt want to shift up to second etc without backing off...

So I changed the autofluid to Full Synthetic and the problems have totally gone...no matter how much hp I now put through it

So for above average hp I would say go for full synthetic...

All the best Brett

928S2 AUTO V8 4.7 LTR 1986 IRIS METALLIC BLUE WITH X-PIPES, RMB, PROMAX CHIPS, KICKDOWN SWITCH, K&N,
PCGB - 928 - FORUM - MODERATOR. WIZARDS OF NOS 1000 HP PRO RACE NITROUS SYSTEM.
EMAIL : managingdirector@pchealthcare.co.uk

RyanPerrella

and what if he doesn't have a 10 million HP car?

I think the benefit of synthetic is it wont break down (as fast) I think the idea that its slicker is a myth. This has always been the reason you don't put synthetic motor oil in older cars cause "oh its going to leak cause its so slick" and what not. Is synthetic motor oil really any slicker? If its leaks past seals it has to be a smaller molecular compound, is it? I don't know. I don't think you should stray from synthetic ATF like mobil one or Redline because you think it is too slick though. If it slipped it wouldn't be a very good fluid, because its still around i doubt thats the case.

Most auto makes use a synthetic ATF now. I know an old 540 i had was fillled with some ultra expensive crap, was supposed to be "lifetime fluid" but that stuff was crap and those transmissions were always going out around 80-120K miles. Run Synthetic ATF, but dont leave it in forever, only BMW would recommend that. EDIT: Actually i am sure the fluid was good stuff, but would have been better stuff had it been changed on a scheduled interval as opposed to just "lifetime"

David L. Lutz

I know when I run mine hard, especially with "brake on starts" it burns the normal Dextron fluid (turns a very dark burnt color) . I am thinking to change to synthetic. Thats what the guy at edgeracing is recommending. (he is modifing my converter as we speak)

Bill Ball

The PO of my car used dino tranny fluid. Since the 90K mile change, I've been using synthetic (M1) for about 100K miles with one change in the middle that was dino-based. Tranny shifts as well as ever despite all the abuse I pile on. I can't say I felt any difference at all between dino and synthetic, but I have no tranny fluid temp monitoring or other information other than shift behavior. At one point I had a sticky 1-2 shift valve (no drop into first gear), and a fluid change made no difference going from dino to synthetic. That cleared up with a tranny cleaning additive with no change in the quality of the shifts.

I understand that some trannies that have never had the fluid changed for say 100K+ miles suffer sometimes after it is changed, be it dino or synthetic, but I see no problem with synthetic replacing dino in a tranny with a record of good maintenance, as long as it meets Dexron II/III specs.

Synthetic ATF is more stable at high temperature, as is true with synthetic oil versus dino. I do some pretty stressful desert driving 2-3 times a years, and w/o any monitoring of my tranny, I decided to go with synthetic. The fluid never has looked or smelled bad at my 30K mile changes and the pan is clean as a whistle.

soupcan

IMHO most transmission related flush/change transmission death stories are BS. People finally service the transmission after 100,000+ miles and something doesn't feel right, then change the fluid with the most expensive fluid they can find. The trans dies anyway, and the fluid is to blame, not the lack of service. Heat is the killer of auto's, heat will break down transmission fluid over time. Change the fluid regularly and all will most likely be well for a long time.

Ed Scherer

I put Mobil 1 ATF in my '90 about 20 thousand miles ago.

Can't say I noticed any difference one way or another.

Brett928S2

Hi

I didn't say it would improve his car...

All it has done on mine is get rid of the overheating fluid problem, apart from that my box acts exactly the same as with ordinary fluid...

All the best Brett

RyanPerrella

Brett,

I just wanted to say 10 million HP, thats all

JHowell37

The reason leaks tend to develop after a switch to synthetic is because most folks fail to mention that prior to going to synthetic, the oil hadn't been changed in 25,000 miles. The new oil contains detergents that break down gaskets that are already failing from neglect and the acids and other by-products that are formed over time.

As far as the trans goes, I'm not sure if they use detergents or if it's just a special hydraulic fluid. Again, any failure that happens shortly after a service is probably a failure that was going to happen anyway.

My family thinks I'm crazy because I'm very meticulous about vehicle maintenance. I usually reply with "who else has had an automatic transmission last over 200,000 miles" but that seems to fall on deaf ears.

Doug Hillary

Hi,
most ATFs have had a significant "synthetic" component in their formulation for many years - and even before the 928 was thought about

Fully synthetic ATFs tend to reduce the operating temperature by a reasonable amount which does extend seal, frictional elements and valving life

Dexron 3 ATFs that also have Euro Approvals (such as Voith, ZF, MB etc) tend to work better with the frictional elements contained in a 928's MB Autobox

Checking for an ATF that meets both MB 236.8 and ZF TE-ML 14 standards may give the best results

I have used Castrol's excellent fully synthetic "Transmax Z" with great results - I don't think that this is available in the US

Mobil 1 Synthetic ATF has a good reputation and a variant of this (under ESSO's banner) is a factory fill in many Euro Auto transmissions. I can't comment on it in a 928 but Bill obviously thinks its OK!

"Flushing" an AutoTrans can cause some issues and a complete drain and new filter is a safe bet

dr bob

I swapped the original fluid in my '89 S4 for Mobil-1 synthetic atf at about 30k miles on the car. I had been using it in my tow vehicle for years with excellent results, so it was a natural to put in the 928. The results were noticeable, in that shifts were firmer with the M-1. I used a 928 Int'l-supplied filter and gasket kit, torqued the pan to specs, and replaced the o-ring in the reservoir tube at the same time. No leaks. I changed back to not-quite-full-synthetic Chevron-branded ATF at the next change (at 60k) mostly to get the shifting back to its less-harsh previous levels. It worked. Keep in mind that I drive the car very gently; If I was looking at more ponies, even DE sessions, I'd put the synthetic back in in a heartbeat. At both changes, the old fluid looked a lot like the new fluid, with no evidence of wear. Fluid was just slightly darker coming out, but no burned fragrance and no stray bits in the sump either.

There are of course some horror stories about using synthetic ATF. I know of one owner in Phoenix who ended up getting a new trans from Porsche after a synthetic fluid change affected shifting pretty seriously after a few days.


The Chevron fluid I have in there now came from Costco and was very reasonably priced. It says "syn" on the case, and is probably synthetic to some degree. At 1/6 the cost of M-1 and for the way I drive, it seemed the best choice.

Brett928S2

Hi

Lolllll....give me a few years and maybe you can say it again

All the best Brett

cold_beer839

Thanks for the info guys.

I'll go with the Red Line synthetic ATF.

Just drove the car tonight, and it is very noticably slow in shifting from 1st to 2nd when leaving from a dead stop under any throttle conditions (easy does it or hammer down).
As the tarns heats up after a few miles, this goes away completely and the trans shifts fine. I have read that synthethic ATF's will cure cold shift issues, which I believe this is.